1. Field of the Invention
This invention relates to an oil-extracted product of indigo naturalis and a process for preparing the same. This invention also relates to a pharmaceutical composition comprising said oil-extracted product, and a method for treating psoriasis, in particular skin psoriasis and nail psoriasis, in which the use of said oil-extracted product is involved therein.
2. Description of the Related Art
Psoriasis is a chronic inflammatory skin disease that may appear on the skin at any area of the body, in particular head, limbs, elbows, knees, etc. Red papules or plaques having clear borders are frequently observed on the skins of psoriasis patients, and the surfaces of the skin lesions of the patients may be covered by silvery-white scales. Some psoriasis patients may even develop arthritis or other symptoms at the same time.
According to skin symptoms, psoriasis is clinically classified into the following four types: chronic plaque psoriasis, guttate psoriasis, erythrodermic psoriasis, and pustular psoriasis. Chronic plaque psoriasis, also known as vulgaris psoriasis, is most commonly seen amongst all the types of psoriasis, and around 80%-90% of psoriasis patients belong to this type. Guttate psoriasis is characterized by numerous small pink or red teardrop-shaped lesions on patients' skins and usually occurs in children from age 7 to age 10, in which most of the patients are found to have suffered a streptococcal infection one or two weeks before the onset of the disease. Erythrodermic psoriasis is characterized by the appearance of erythema or exfoliation over the whole body's surface or more than 90% of the body's surface, and under more severe conditions, the occurrence of itching over the whole body, which may be further accompanied by fever and malaise. Moreover, generalized acute pustular psoriasis may even be induced in patients with erythrodermic psoriasis. Pustular psoriasis can be further categorized into generalized pustular psoriasis and localized pustular psoriasis (e.g., pustulosis palmaris et plantaris and acrodermatitis perstans). Besides, around 10% of the psoriasis patients have a complication of psoriatic arthritis, which is a CD8 T cell-driven autoimmune inflammatory disorder that affects ligaments, tendons, fascia, and spinal or peripheral joints, while up to 90% of the patients have suffered nail psoriasis.
Due to the complicated pathological conditions and symptoms involved therein, the pathogenesis of psoriasis has yet to be well understood to date. Some studies have revealed that inheritance plays an important role in the pathogenesis of psoriasis, and trauma, infection, stress, endocrine factors, metabolism factors, weather and medication may induce or aggravate psoriasis. After the onset of psoriasis, this disease may recur repeatedly over patients' lifetime and no eradication of the same is possible.
The conventional treatments for psoriasis are generally designed according to the age, gender, occupation and cognitive ability of the patient, the types and distribution of lesions, patient's response(s) to previous therapeutic method(s), and other medical histories of the patient. The primary therapeutic methods for psoriasis include topical therapy, systemic therapy, injection of biologics and phototherapy. Compositions for topical therapy include, e.g., corticosteroids, anthralin (available as Margiton®), coal tar (available as Polytar®), calcitriol (available as Silkis®), tazarotene (available as Tazorac®), salicylic acid, etc., and these compositions are suitable for treating psoriasis patients with mild symptoms. Oral preparations of methotrexate (MTX), cyclosporine, retinoids, etc., are commonly used for systemic therapy and are suitable for treating psoriasis patients with medium to severe symptoms. Biologics include alefacept (available as Amevive®), efalizumab (available as Raptiva®), etanercept (available as Enbrel®) and adalimumab (available as Humira®), and they are suited for injecting into psoriasis patients with medium to severe symptoms. Phototherapy, e.g., ultraviolet B (UVB) phototherapy, photochemotherapy such as psoralen plus ultraviolet A (PUVA), etc., is suitable for treating psoriasis patients with severe symptoms.
However, long-term use of the conventional treatments described above may result in serious side effects or drug tolerance, thereby further reducing patient compliance. In view of the foregoing, many researchers have attempted to explore, from traditional Chinese medicines (TCM), active components that can be used to treat psoriasis.
Indigo naturalis (also referred to as natural indigo; Chinese: Quing dai) is a dark-blue plant pigment extracted from leaves of an indigo-producing plant such as Baphicacanthus cusia (Nees) Bremek., Polygonum tinctorium Lour., Isatis indigotica Fort., etc. Indigo naturalis is known in TCM to have heat-clearing and blood-cooling effect, and it has been clinically used to treat chronic myeloid leukemia, psoriasis, mumps, various ulcers (e.g., peptic ulcers, oral ulcers, etc.), hepatitis, herpes zoster and otitis externa.
It has been known that various active components can be isolated from indigo naturalis prepared from different indigo-producing plants, amongst which the most common active components are indigo, indirubin, isoindigo, etc. It has been reported that indirubin has anti-tumor, anti-inflammation, and immunomodulatory effects and has been considered to have potential in the treatment of chronic myelocytic leukemia (G. Eisenbrand et al. (2000), J. Cancer Res. Clin. Oncol., 130:627-635; T. Kunikata et al. (2000), European Journal of Pharmacology, 410:93-100; N. K. Mak et al. (2004), Biochemical Pharmacology, 67:167-174; S. Leclerc et al. (2001), The Journal of biological Chemistry, 276:251-260).
Indigo naturalis has been reported to have poor water solubility and, hence, not a few researchers have aimed at extracting the active components contained therein using organic solvents. Q. S. Zhang et al. used four different organic solvents, i.e., 75% ethanol, chloroform, ethyl acetate and acetone to extract indigo naturalis, with/without a preliminary 36% HCl treatment, and the indirubin contents of the products thus obtained were determined and compared. The obtained experimental results reveal that regardless of being subjected to the preliminary 36% HCl(aq) treatment or not, the ethyl acetate-extracted product has a highest indirubin content, followed by the acetone-extracted product, the chloroform-extracted product and the 75% ethanol-extracted product. Besides, the preliminary 36% HCl(aq) treatment significantly increases the indirubin content in each organic solvent-extracted product (Q. S. Zhang et al. (2006), Journal Guangxi Normal University: Natural Science Edition, 24(3):58-60).
In previous studies, the applicants developed an indigo naturalis composite ointment formulated by 20% (by weight) indigo naturalis powder and 80% vehicle (containing 25% Vaseline, 30% yellow wax and 45% olive oil), and investigated the use of said ointment as a topical treatment for psoriasis. The applicants found that topical application of said ointment was effective in treating pediatric psoriasis, recalcitrant psoriasis and plaque-type psoriasis (Y. K. Lin et al. (2006a), Pediatric Dermatology, 23(5):507-510; Y. K. Lin et al. (2006b), Clinical and Experimental Dermatology, 99-100; and Y. K. Lin et al. (2007), Dermatology, 214:155-161).
In a subsequent study, the applicants used an indigo naturalis ointment formulated by indigo naturalis powder and the vehicle described above at a ratio of 1:10 (by weight) to treat outpatients with chronic plaque psoriasis and found that topical application of said ointment resulted in significant reductions in the scaling, erythema and induration scores as well as plaque area percentage (Y. K. Lin et al. (2008), Arch Dermatology, 144(11):1457-1464).
The applicants further investigated the anti-psoriatic effect of indigo naturalis on the proliferation and differentiation of keratinocytes, in which an indigo naturalis sample, which was obtained by dissolving indigo naturalis powder in dimethylsulfoxide (DMSO) in a proportion of 1:10 (w/v), followed by sterilization by filtration (pore size 0.2 μm), and the two major components of indigo naturalis, i.e., indigo blue (purchased from Fluka, Bucks, Switzerland) and indirubin (purchased from Alexis, Lausen, Switzerland), both being dissolved in DMSO before dilution in culture medium, were tested in the bioassays. The obtained results reveal that the anti-psoriatic effects of indigo naturalis are mediated, at least in part, by modulating the proliferation and differentiation of keratinocytes, with indirubin as the major active component (Y. K. Lin et al. (2009a), Journal of Dermatological Science, 54:168-174).
The applicants further investigated the anti-inflammatory effects of said indigo naturalis sample and indigo blue and indirubin, as well as tryptanthrin, in human neutrophils, and found that only said indigo naturalis sample inhibits human neutrophil proinflammatory responses, including respiratory burst and degranulation, which were mediated through blocking MAPK and Ca2+ signaling pathways. The obtained results support the concept of developing a whole herbal extract of indigo naturalis, rather than the major component(s) contained therein, for treating neutrophilic inflammation (Y. K. Lin et al. (2009b), Journal of Ethnopharmacology, 125:51-58).
While organic solvents have been used to extract indigo naturalis, the products thus obtained may contain trace amounts of said organic solvents which may cause adverse effects to human body. The indigo naturalis ointment as previously developed by the applicants has the drawbacks of unpleasant odor and deep blue color that may leave stains on nails, skins and clothes, thereby affecting patients' compliance.
Therefore, the applicants developed a new formulation in which indigo naturalis powder is refined by an oil extraction, in particular by olive oil extraction, so that the major component of indigo naturalis, i.e., indigo blue, as well as impurities such as lime, is removed. This new formulation reduces the blue discoloration of nails, skins and clothes and provides less skin irritation, thus rendering psoriasis treatment more user-friendly.